Energy changes

Question 1

What is an exothermic reaction

Answer 1

When energy is given out to the surroundings

Question 2

What is an endothermic reaction

Answer 2

When energy is taken in from the surroundings

Question 3

If rectants have more energy than products, what type of reaction is it

Answer 3

Endothermic

Question 4

What is breaking bonds
Exo or endo

Answer 4

Endothermic

Question 5

What are two examples of an exothermic reaction

Answer 5

Burning fuels- Combustion
Neutralisation (Acid + Alkali–> Salt + Water)

Question 6

What is an example of an endothermic reaction

Answer 6

Thermal decomposition

Question 7

What is a real life use of exothermic reactions

Answer 7

Instant hand warmers

Question 8

What is a real life use of endothermic reactions

Answer 8

Instant sports ice packs

Question 9

If there is an exothermic reaction on a graph, will the line be above or below the initial point

Answer 9

Below

Question 10

What is the peak amount of energy reached during a reaction called

Answer 10

Activation energy

Question 11

What do you need to break bonds

Answer 11

Energy/ heat

Question 12

What is released when new bonds form

Answer 12

Energy

Question 13

What is an electrochemical cell

Answer 13

A system where there are two different electrodes in contact with an electrolyte.

Question 14

What are the electrodes typically made out of

Answer 14

Metals

Question 15

What is an electrolyte

Answer 15

A liquid that is able to carry charge. It contains ions that react with the electrodes

Question 16

How does a simple battery work

Answer 16

The chemical reactions between the electrodes (which are connected at the top) and the electrolyte set up a charge difference between the electrodes.

This means electricity will flow from the more reactive metal to the less reactive metal.

Question 17

What does the voltage of a cell depend on

Answer 17

• The metals used
• The type of electrolyte

Question 18

What is a battery and how do you make one

Answer 18

A battery is two or more cells connected in series
You can make a battery by connecting different cells

Question 19

Why do sime batteries run out of charge

Answer 19

Because all of the reactants are used up and the reaction is irreversible

Question 20

What type of batteries are non rechargeable and why

Answer 20

Alkene batteries are non renewable
This is because te reaction is irreversible

Question 21

How are rechargeable batteries recharged

Answer 21

The reaction is reversed by connecting an external electric current

Question 22

What is a fuel cell

Answer 22

An electrical cell that is supplied with fuel and oxygen
Uses energy from the reaction to produce electrical energy

Question 23

What happens to fuel when it enters the fuel cell

Answer 23

The fuel is oxidised. This sets up a potential difference within the cell

Question 24

What are the reactants and products in a hydrogen fuel cell

Answer 24

Reactants:
Hydrogen and oxygen
Products:
Water and energy

Question 25

How is a hydrogen fuel cell set up

Answer 25

Electrolyte (potassium hyroxide) in the middle Carbon Anode (negative) on the left Carbon Cathode (positive) on the right REVERSE OF ELECTROLYSIS Both electrodes have inlets on the sides Hydrogen goes into anode Oxygen goes into cathode All water and heat leaves through outlet of cathode

Question 26

How does a hydrogen fuel cell work

Answer 26

Hydrogen comes in and is oxidised by anode Hydrogen becomes an ion Electrons pass around the wire to the cathode, while the hydrogen moves through the electrolyte to the cathode Electrons and hydrogen ions react with oxygen to produce water Water leaves by outlet

Question 27

What is the half equation of oxidation of hydrogen in fuel cells

Answer 27

H₂ ---> 2H(+) + 2e(-)

Question 28

What is the half equation of the reaction of hydrogen ions and water at the positive electrode

Answer 28

O₂ + 4H(+) + 4e(-) --> 2 H₂O

Question 29

What is the overall equation in a fuel cell

Answer 29

2H₂ + O₂ ---> 2H₂O

Question 30

What are some advantages of hydrogen fuel cells

Answer 30

- Less polutants/ emissions - More reusable than electric batteries - Cheaper than electricc batteries - Can store more energy than typical batteries

Question 31

What are some disadvantages of hydrogen fuel cells

Answer 31

- Hydrogen is a gas so it takes up more space - Hydrogen is explosive so must be handled with care - Hydrogen is made from electrolysis which uses energy that could be releasing emissions